Outline

Advances in the field of tissue engineering offered new alternatives for cartilage repair therapies. For the completely autologous in vitro formation of human cartilaginous tissue for subsequent transplantation we developed an completely autologous 3D culture system where human articular chondrocytes cultured in the presence of autologous serum. Chondrocytes form a 3-dimensional chondrocytic tissue by generating their own extracellular matrix that is similar to the body’s natural hyaline cartilage. Here, demands on in vitro engineered tissues as the capacity to adhere and integrate as well as to remodel after contact with native tissues were evaluated.

Chondrocytes were isolated from patients undergoing articular arthroplastic surgery and cultured in monolayer followed by condensing chondrocytes to 3-dimensional chondrocytic spheroids. Chondrospheres were placed on cartilage explants of cartilage chips from osteoarthritic knees and cultured for up to 8 weeks. Adhesion and integration characteristics were studied histological after paraffin embedding; remodelling and maturation processes were characterized using immunohistochemical staining for articular cartilage-specific markers.

Immediate adhesion of chodrospheres is mediated by cell-matrix contacts of surface chondrocytes of chodrospheres. Additionally, adhesion and integration is mediated by migration of surface cells out of chondrospheres into fissures of native cartilage structures. De novo synthesized matrix of migrated cells fills the fissures and is immunohistochemically stained for respective cartilage specific markers.

Adhesive and integrative capacity of chondrocytic spheroids meets on of the most important demands on in vitro engineered tissues. Adhesion and integration are mediated by chondrocytes itself and characterize the first step for a possible therapeutic action. More important, integration is accompanied by full integration of de novo synthesized, specific chondrogenic matrix presenting the remodeling capacity of chondrospheres. Further studies have to be done to characterize these processes under in vivo conditions.